In the typical inkjet printer, ink is disposed in a plurality of ink chambers formed in respective ones of a plurality of nozzles belonging to a print head. An orifice in communication with the chamber opens onto a receiver medium which receives ink droplets ejected from the orifice. The means of ejection may, for example, be a piezoelectric crystal disposed in the nozzle and deformable when subjected to an electric pulse. When the crystal deforms, a pressure wave is produced in the ink in the nozzle, which pressure wave ejects one or more ink droplets. Other types of inkjet printers include heaters situated below the orifice for creating a steam bubble which, when activated, propels ink through the orifice and onto the surface of the receiver media. Inkjet printing has become recognized as a prominent contender in the digitally controlled, electronic printing arena because, for example, of its non-impact, low-noise characteristics, its use of plain paper and its avoidance of toner transfers and fixing.
However, a problem associated with some prior art inkjet printers is blockage and clogging of the nozzle orifice with particulate matter (e.g., dirt, dust, and the like) acquired during use. Such blockage of the orifices is undesirable because blockage of one or more of the orifices gives rise to undesirable image artifacts, such as banding and streaking.
Another problem associated with some prior art inkjet printers is blockage and clogging of the orifice with dried ink. Again, such blockage of the orifices is undesirable because blockage of one or more of the orifices gives rise to undesirable image artifacts, such as banding and streaking.
A type of ink jet printing mechanism is disclosed in U.S. Pat. No. 3,946,398, which issued to Kyser et al. in 1970. This patent discloses a drop-on-demand ink jet printer which applies a high voltage to a piezoelectric crystal, causing the crystal to bend, thereby applying pressure on an ink reservoir and jetting ink drops on demand. However, such piezoelectric printing mechanisms usually require complex high voltage drive circuitry and bulky piezoelectric crystal arrays, which are disadvantageous with respect to manufacturability and performance. Moreover, the Keyser et al. patent does not appear to disclose a printer having mechanically-assisted ink droplet separation and method of using same, for separating an ink meniscus from an ink nozzle orifice while clearing-away particulate matter from about the orifice.
Commonly assigned U.S. patent application Ser. No. 08/750,438 titled "A Liquid Ink Printing Apparatus And System" filed in the name of Kia Silverbrook on Dec. 3, 1996, discloses a drop-on-demand liquid printing system that obtains precise drop size and placement accuracy, high printing speeds, low power usage, durability, low thermal stresses, and other desirable printer performance characteristics, such as ease of manufacture, and use of inks having suitable characteristics. Silverbrook provides a drop-on-demand printing mechanism wherein a means of selecting drops to be printed produces a difference in position between selected drops and drops which are not selected. The application of an electric field or the adjustment of receiver proximity are disclosed as means for causing separation of the selected drops from the body of the ink. However, the electric field strength needed to separate the selected drop is in the neighborhood of the value where breakdown of the drop in air occurs. Therefore, use of an electric field is not preferred. Separation by bringing a roller adjacent to the print head to pick-up selected droplets is unreliable due to presence of relatively large dust particles typically found in an uncontrolled environment. Moreover, the Silverbrook patent does not appear to disclose a printer having mechanically-assisted ink droplet separation, for separating an ink meniscus from an ink nozzle orifice while clearing-away particulate matter from about the orifice.
Therefore, there has been a long felt need to provide a printer having mechanically-assisted ink droplet separation and method of using same, for separating an ink meniscus from an ink nozzle orifice while clearing-away particulate matter from about the orifice.